FIX discard

On any form, if you edit and try to discard you get an error

check this lines:
https://github.com/odoo/odoo/blob/11.0/addons/web/static/src/js/views/basic/basic_controller.js#L82
https://github.com/odoo/odoo/blob/11.0/addons/web/static/src/js/core/dialog.js#L235

web_dialog_size/static/src/js/web_dialog_size.js

@@ -32,7 +32,8 @@ Dialog.include({
                 handle: '.modal-header',
                 helper: false
             });
-        }
+        };
+        return this;
     },
 
     close: function() {